Roman numeral symbols and values
Modern Roman numerals use seven basic symbols: I for 1, V for 5, X for 10, L for 50, C for 100, D for 500, and M for 1000. Values usually run from larger to smaller from left to right and are added together.
For example, LVIII is 50 plus 5 plus 3, so it represents 58. Repeating I, X, C, or M can express consecutive units, but a canonical numeral does not repeat the same symbol more than three times in a row.
How subtractive notation works
A smaller allowed symbol before a larger one is subtracted. The standard pairs are IV and IX, XL and XC, and CD and CM. Thus XLIX is 40 plus 9, or 49.
This converter accepts canonical modern forms rather than every sequence that could be interpreted by simple addition and subtraction. That makes one standard spelling for each supported number and prevents ambiguous inputs.
- Read CM as 900 and XL as 40.
- Read IV as 4.
- Add 900, 40, and 4 to get CMXLIV = 944.
Converting numbers in both directions
To write a number, repeatedly take the largest symbol or subtractive pair that does not exceed the remaining value. For 2024, take MM for 2000, then XX for 20, then IV for 4, producing MMXXIV.
To read a canonical numeral, evaluate each symbol or pair from left to right. A smaller symbol before a permitted larger symbol forms one subtractive pair; otherwise the values are added.
Range, canonical form, and historical variants
The supported numeric range is 1 through 3999, which can be written with the seven standard symbols without an overline convention for thousands. Zero, decimals, negatives, and values above 3999 are outside this tool’s scope.
Roman writing has historical and stylistic variants. IIII appears on some clock faces and is not universally invalid Roman usage, but this converter does not accept it because it validates only canonical modern subtractive notation, where 4 is IV.
Frequently asked questions
How does this roman number converter handle 4 and 9?
It uses canonical subtractive notation: 4 is IV, 9 is IX, 40 is XL, 90 is XC, 400 is CD, and 900 is CM.
What range does the converter support?
It converts whole numbers from 1 through 3999 and accepts the corresponding canonical modern Roman numerals.
Why is IIII not accepted?
IIII is a documented historical or stylistic form, notably on some clock faces. This tool deliberately validates the canonical modern form IV so that each supported value has one standard output.
Can Roman numerals represent zero or decimals?
Not in this converter. It is designed for positive whole numbers from 1 to 3999 in the familiar modern Roman-numeral system.
Is a Roman numeral read from left to right?
Usually yes. Add values in descending order, except where an allowed smaller symbol appears before a larger one, forming a subtractive pair such as IV or CM.
Further reading: Roman numerals, Wikipedia